The invention relates generally to motor drives. Particularly, this invention relates to a protection system implemented in a common bus connection between motor drives.
In many modern automation settings, motors are generally coupled to motor drives configured to control the rotational speeds of the motors. In so doing, motor drives typically comprise components, such as converters, inverters and associated circuitry for controlling motors. Among electrical connections comprising the circuitry in motor drives is the electrical connection between the converter and the inverter of the motor drive, typically referred to as a “DC bus.”
In certain instances it may be desirable to connect two or more motor drives via their respective DC buses. Such arrangements may be advantageous for many reasons, such as to minimize wiring and termination costs upon installation and servicing. Similarly, during operation, some motors may require input power while others may be available to regenerate power, the latter being applied to the common bus to aid in driving the then power-consuming motors. In such a configuration, the motor drives are said to share a common DC bus or to be in a common DC bus mode. A common DC bus mode may be established by connecting the DC bus of two or more motor drives, which could have identical hardware. In establishing a common DC bus connection between motor drives, it may be necessary to define functional modes of operation depending on how the motor drives are positioned in a circuit topology. That is, the configuration of each of the motor drives placed in a common DC connection may depend upon or may dictate how each motor drive in the circuit topology provides to or receives power from the common DC bus.
Given a certain circuit topology, user configurations of the motor drives not in accordance with the circuit topology may damage the motor drives, leading to their malfunction. There is a need, therefore, for a technique that can avoid mis-configuration of motor drives when connected to a common DC bus.